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Stephanie Riviere, a graduate student in Integrative Biology at Laurier, won theIain and Sylvia Taylor Award at “Botany 2012”, an international conference held in Columbus, Ohio in 8-11 July. The award was presented by the Canadian Botanical Association for the best Canadian student poster.

Stephanie studies the function, diversity and evolution of some mysterious formations found in the flower of Cuscuta (dodder) called infrastaminal scales. For a very long time it was believed that these polyp-like structures secrete nectar to attract pollinators, therefore, having a role in the sexual reproduction of these plants. Stephanie, however, found that scale characteristics are not correlated with the breeding system in the over 150 species that she has examined. Instead, based on the strategic placement of the IFS around the ovary and their morpho-structural adaptations, she proposed that these formations have a defense role. Each of the polyp-like elaborations of the scales contain a laticifer cell that secretes a lipid-based resin. The laticifer cell is surrounded and protected by an epidermis, except at its tip which remains exposed. The slightest touch, for example by an insect, determines the laticifer cell to burst open and release the latex. The role of these “landmine” cells is to provide a defense layer against herbivorous insects that may want to feed on the ovules/seeds found in the center of the flower. Stephanie’s hypothesis is also corroborated by feeding assays done in collaboration with De Moraes lab from Penn State University, which have shown that the latex is toxic to various insect larvae.

A couple of other students in the Costea lab have participated to this project. As a part of her Honors Thesis, Courtney Clayson did a general floral developmental study, which provided data about the timing of initiation of these structures in relationship to other floral parts. Last but not least, Kristy Dockstader dissected, extracted and imaged scales from thousands of flowers. Keep in mind that these formations are usually smaller than 1 mm!